图像引导放射治疗通过精准的患者定位，实现尤其符合肿瘤的照射。这已经成为放疗的标准方法，其增加了患者的成像剂量。Halcyon 3.0 直线加速器（Varian Medical Systems，加利福尼亚州帕洛阿尔托）由于其几何结构需要每日成像，因此该加速器配备了在线 kV 和 MV 成像。然而，照射所需的每日 CBCT 影像应用了额外的辐射，这增加了正常组织的剂量，因此可能影响患者的二次癌症风险。在本研究中，实际器官剂量被测量了 kV 系统，同时呈现了所有可用 kV CBCT 协议的正常组织剂量比较，以展示实体和协议之间成像剂量的差异。此外，本文还评估了成像的有效剂量和二次癌症风险。实验采用热释光剂量计对一个类人的仿生测量模型进行了测量，该模型按每个实体位置（大脑、头颈、乳房、肺、盆区）定位。使用所有可用的预设协议获取 CBCT 影像，无需进一步调整参数。然后比较每个位置和每个协议的测量剂量，并计算相关和特别放射敏感器官的二次癌症风险。结果发现，使用相应的快速和低剂量模式，如 Pelvis 和 Head 协议，成像剂量可降低高达一半。另一方面，较大的场尺寸或 Large 模式会产生比其初始协议更高的剂量。Image Gently 被发现是最能保护正常组织的协议，但由于影像质量低或投影数据不足，不适用于某些实体。通过使用适当的 kV-CBCT 协议，可以显著降低成像剂量，从而节约健康组织。结合影像质量研究的研究，本研究的结果可能导致有关每日常规中选择的协议的工作流程的调整，从而防止不必要的辐射暴露并减少二次癌症风险。版权所有 © 2023 The Author(s)。由 Elsevier GmbH. 发布。保留所有权利。

Image guided radiotherapy allows for particularly conformal tumour irradiation through precise patient positioning. Becoming the standard for radiotherapy, this increases imaging doses to the patient. The Halcyon 3.0 linear accelerator (Varian Medical Systems, Palo Alto, CA) requires daily imaging due to its geometry. For this reason, the accelerator is equipped with on-line kV and MV imaging. However, daily CBCT images required for irradiation apply additional radiation, which increases the dose to normal tissue and therefore can affect the patient's secondary cancer risk. In this study, actual organ doses were measured for the kV system, and a comparison of normal tissue doses for all available kV CBCT protocols was presented to demonstrate differences in imaging doses across entities and protocols. In addition, effective dose and secondary cancer risk from imaging are evaluated.Measurements were performed with thermoluminescent dosimeters in an anthropomorphic phantom positioned according to each entity (brain, head and neck, breast, lung, pelvis). CBCT images were obtained, using all available pre-set protocols without further adjustment of the parameters. Measured doses for each position and each protocol were then compared and secondary cancer risk of relevant and specifically radiosensitive organs was calculated.It was found that imaging doses for protocols such as Pelvis and Head could be reduced by up to half using the corresponding Fast and Low Dose modes, respectively. On the other hand, larger field sizes or the Large mode yielded higher doses than their initial protocols. Image Gently was found to spare normal tissue best, however it is not suitable for certain entities due to low image quality or insufficient projection data.By using appropriate kV-CBCT protocols, it is possible to reduce imaging doses to a significant extent and therefore spare healthy tissue. Combined with studies of image quality, the results of this study could lead to adjustments in workflow regarding the choice of protocols used in daily routine. This could prevent unnecessary radiation exposure and reduce secondary cancer risk.Copyright © 2023 The Author(s). Published by Elsevier GmbH.. All rights reserved.